There is an instrument that I like alot and I have been hearing in a couple of songs, but I cannot figure out what the instrument is. Let me start with what it sounds like. I *believe* it's some kind of organ, and you can hear it the best at about :59 in this video (The song is Gena's theme by the Bee Gees, it's where I first heard the instrument): http://youtu.be/MgtYBhx-__Q?t=59s

It's that distinctive, warbling, organ sound that is heard droning (not in a bad way) in the background.

The only other place I have heard it is, once again, providing background harmony in the controversial C418 'Chirp' minecraft song, however, when I try and find information about the instrument as heard in Chirp, all I get is references to the Optigan and Little Big Planet. I can't search based on it being used in Gena's Theme because it's to obscure :/

If timeline information might help, I do know these things:

"[The song] is a rare instrumental by the Bee Gees. Colin and Maurice on bass and drums, Barry on rhythm, Vince on lead, and even Robin on ORGAN, all overlaid with an orchestral section arranged by Bill Shepherd"

Thanks for the replies guys, I think I have narrowed it down to the Hammond with the rotating speaker. I got a decent VST Hammond B3 plugin with simulated rotating Leslie speaker, and with upper vibrato enabled I can reasonably accurately simulate the organ sound I was hearing.